Molecular defects of the extracellular matrix are being sought in human connective tissue disorders. Of particular interest are those inborn diseases that affect the musculoskeleton, the more common being the Ehlers-Danlos syndromes and osteogenesis imperfecta. A rich source of rare tissues is available to us at Children's Hospital Medical Center and an extensive freezer collection is established and continues to be built upon. The main approach is direct analysis of these tissue biopsies using biochemical techniques and electronmicroscopy. Though a portion of effort is spent screening promising new cases, the main effort is focused on selected individual cases in which molecular amomalies are indicated. Of principal interest are collagen disorders, though proteogylcan defects could be revealed. A primary objective is to gain insight on the structure and function of collagen impossible by study of normal tissues, with the long-term goal and potential side goals of detecting, treating and preventing these skeletal disorders. Collagen crosslinking receives careful attention. Impaired crosslinking is a critical factor in several of the identified diseases of the collagen molecule, and many other defects of crosslinking seem likely. Discoveries during the first project period to be persued include: 1. Ehlers-Danlos VI: Despite a normal content of hydroxylysine, type II collagen revealed a grossly abnormal crosslinking chemistry. 2. Three patients, one phenotypically an Ehlers-Danlos VII, a second with Ehlers-Danlos I and a third with Noonan's Syndrome revealed extended Alpha1(I) chains on electrophoresis of skin and tendon extracts. The data indicate a new molecular disease of collagen in which collagen molecules bearing incompletely cleaved Alpha1(I) carboxy-propeptides persist in the extracellular matrix. 3. Bone matrix from a dominant case of osteogenesis imperfecta showed a high ratio of Alpha1(I) to Alpha2 chains in pepsin extracts, pro-Alpha1(I) chains in denaturant exptracts and, by electronmicroscopy, abnormal osteoblasts with accumulated matrial in distended cisternae of the rough endoplasmic reticulum. Many inborn disorders impair the structure and development of the skeleton. They account for a significant fraction of the 12 milion Americans who have birth defects. Defects in collagen production are likely to account for many of these diseases.